(CNN) -- Rising public anger over the oil disaster in the Gulf of Mexico hit the boiling point Thursday as BP CEO Tony Hayward was subjected to a bipartisan barrage of criticism during a long, heated day of testimony on Capitol Hill.

"I think the evasiveness of your answers only served to increase the frustration -- not decrease the frustration -- [of] not just of members of Congress, but that of the American people," said Rep. Bart Stupak at the end of the House Energy and Commerce Committee's Subcommittee on Oversight and Investigations hearing.

Democrats and Republicans alike repeatedly accused the embattled British corporate chieftain of refusing to answer their questions, cutting corners on safety, and turning a blind eye to mounting scientific evidence of an unprecedented environmental tragedy.

Hayward, testifying before the committee, apologized for the April 20 Deepwater Horizon explosion and continuing oil spill but insisted that it was "too early" to reach conclusions about whether BP had cut corners on safety.

"If there's any evidence that anybody put costs above safety I will take action," he said.

I can't believe you said that," retorted Rep. Henry Waxman, D-California and chairman of the House Energy and Commerce Committee. "Of course there's evidence."

"Your testimony continues to be at odds to all independent scientists," Rep. Ed Markey, D-Massachusetts, said when Hayward refused to directly answer a question about whether large underwater plumes of oil are lurking in the Gulf.

Public angst over the spill was evident, with a tar-stained protester being removed by police after screaming that Hayward needs "to be charged with a crime." The protester was charged with unlawful conduct for disrupting Congress.

The hearing was not devoid of partisan controversy. Gingrey argued that the full story of the disaster was not being told because no one from the administration was testifying on whether there had been lax government oversight over BP.

And Rep. Joe Barton, R-Texas, opened Republican statements with an apology to Hayward, saying he was "ashamed" that the company has been subjected to what Barton characterized as a $20 billion "shakedown" by the administration.

"I think it is a tragedy of the first proportion," said Barton, whose district includes Houston, site of BP's U.S. headquarters.

Barton was referencing Obama's announcement Wednesday that BP had agreed to set aside $20 billion in an escrow account to compensate oil spill victims. BP also agreed to create a $100 million fund to compensate oil rig workers now unemployed as a result of closure of other deepwater rigs after the April 20 Deepwater Horizon explosion.

Barton's comment sparked a firestorm of criticism throughout the day. White House Press Secretary Robert Gibbs released a statement saying that "Joe Barton seems to have more concern for big corporations that caused this disaster than the fishermen, small-business owners and communities whose lives have been devastated by the destruction."

Several Republicans blasted Barton as well. Rep. Jeff Miller, R-Florida, said in a written statement that he was shocked by the congressman's "reprehensible comments" and called on him to give up his post as the committee's ranking Republican.

Barton later backtracked from his statement with both a verbal and written apology.

"I apologize for using the term 'shakedown' ... and I retract my apology to BP," he said in the written statement. "BP should bear the full financial responsibility for the accident on their lease in the Gulf of Mexico. BP should fully compensate those families and businesses that have been hurt by this accident."

During the hearing, Hayward tried to strike an apologetic tone before the committee.

"We will not rest until we make this right," he said, a theme of a widely used BP television advertisement. "We're a strong company and no resources will be spared."

"When I learned that 11 men had lost their lives in the explosion and fire on the Deepwater Horizon, I was personally devastated," he said. "I want to offer my sincere condolences to their family and friends."

Hayward, who began his testimony by waiving his right to legal counsel, indicated in his prepared statement that he does not know whether BP's efforts to stop the gushing oil will succeed soon.

"We cannot guarantee the outcome of these operations, but we are working around the clock with the best experts from government and industry," he said.

Hayward noted that the drilling of two relief wells, "which we believe represents the ultimate solution to stopping the flow of oil and gas from the well," has now reached depths of 15,226 feet and 9,778 feet, respectively. They are not expected to be completed until August.

"We have spent nearly $1.5 billion so far, and we will not stop until the job is done," he said.

Though the company has accepted that it is the "responsible party," Hayward added a qualification: "It is important to understand that this 'responsible party' designation is distinct from an assessment of legal liability for the actions that led to the spill," he said.

Hayward repeatedly refused, however, to speculate "on what may or may not have made a difference" in preventing the disaster until ongoing investigations are completed. Pressed for a direct answer on whether BP has made good on a commitment to safety that was pledged when he became CEO three years ago, Hayward would not give a clear yes or no answer.

"We have focused like a laser on safe and reliable operations," he said. "We have made major changes."

Waxman sharply criticized Hayward's response.

"It's clear to me you don't want to answer any of our questions," Waxman said. "I am amazed at this testimony. You're kicking the can down the road. I find that irresponsible."

"I am not stonewalling," Hayward said. "I was simply not involved in the decision-making process [for Deepwater Horizon]. ... I won't draw conclusions until an investigation is concluded."

Frustration with both BP and the federal government has been rising in the weeks since the explosion. Billy Nungesser, president of Louisiana's southern Plaquemines Parish, said Thursday that Coast Guard Adm. Thad Allen, the government's oil disaster response manager, should step down from that post.

Allen replied that he has "been in public service for a long time" and serves "at the pleasure of the president."

Also, Interior Department Inspector General Mary Kendall testified about regulations governing the oil industry during an appearance on Capitol Hill on Thursday. Among other things, she called the regulations guiding the government investigation of the oil spill "completely backwards."

Appearing before the House Subcommittee on Energy and Mineral Resources, Kendall questioned the training and supervision of inspectors at Interior's scandal-plagued Minerals Management Service, which is responsible for overseeing oil drilling.

"We have been told that MMS has approximately 60 inspectors for the Gulf of Mexico region to cover nearly 4,000 facilities," she said. "This is juxtaposed with the Pacific Coast, which has 10 inspectors for 23 facilities."

The agency has trouble hiring inspectors, she said, because oil and gas companies pay more. The inspectors train using guidelines and instructions that "appear to be considerably out of date," she said.

In late May, MMS Director Elizabeth Birnbaum left the agency under a cloud after a series of allegations of misconduct by MMS employees. A report by the Interior Department's inspector general revealed that federal inspectors overseeing oil drilling in the Gulf of Mexico accepted meals and tickets to sporting events from companies they monitored between 2005 and 2007.

Interior Secretary Ken Salazar has called the allegations of MMS corruption "evidence of the cozy relationship between some elements of [the agency] and the oil and gas industry."

Among other things, MMS regulators failed to follow regulations on blowout preventers on drilling rigs, according to a Wednesday letter from Iowa GOP Sen. Charles Grassley to BP Chairman Lamar McKay.

Grassley said in the letter, obtained by CNN, that he found it "very disturbing that BP asserts that the 'practice' in oil drilling is to avoid current laws to keep our beaches safe."

"And I am outraged that MMS is looking the other way," Grassley said in the letter.

MMS did not immediately respond to a request for comment from CNN. Acting MMS Director Bob Abbey told members of the House subcommittee Thursday that the Gulf spill has forced everyone involved with offshore drilling to reconsider their preparedness for a disaster.